Elevators are generally employed in casing, drilling, and other wellbore operations to hoist and lower tubulars (e.g., casing or drill pipe) into the wellbore. The elevators may be coupled to a travelling block of the rig, and maneuvered to engage and hoist a tubular. The tubular is then brought into position and attached (“made up”) to a lower tubular, which is already positioned in the wellbore, and then lowered. One common type of elevator employs slips that support the tubular by biting into or otherwise engaging the outer diameter of the tubular. Slip-type elevators generally include a “bowl” and several slips, which can be circumferentially spaced apart. When the elevator is disposed around a tubular, the slips can be lowered into the bowl, thereby adjusting the slips to move radially inward into engagement with the tubular. Downward force on the slips from the weight of tubular/tube string provides the gripping force for the slips.
This arrangement has proven effective in a variety of different applications. However, during running operations, it is not uncommon for the tube string to catch on a wellbore impediment. The rig operators may be unaware of the instant such catching occurs, and thus the elevator may continue to be lowered as the tube string is temporarily supported on such an impediment. Accordingly, the elevator may be relieved of the weight of the tube string, which, as noted, the elevator uses to provide the gripping force. This situation can lead to a drop of the tube string, which can be costly, or even catastrophic, to wellbore operations.
Attempts to address this potential have met with challenges. For example, existing devices useable to lock elevator slips into place generally require one or more manual adjustments and/or calibrations prior to use, to accommodate the diameter of the elevator and/or the tubular to be gripped. This introduces an additional potential for human error, takes valuable time in the running process, and generally does not permit lowering of the slips to engage a tubular while the locking devices themselves are operatively engaged.
What is needed, therefore, is an improved apparatus and method for limiting slip movement in an elevator.